1. Field of the Invention
The present invention relates to a projection-type display device. More specifically, the present invention relates to a technique for radiating heat generated by a light source.
2. Related Background Art
FIG. 13 is a schematic cross-sectional view showing a configuration of a projection-type display device D5.
The projection-type display device includes a total reflection mirror 5, a screen 6, a housing 50, and a projection unit 20.
FIG. 14 is a schematic view showing a configuration of the projection unit 20.
The projection unit 20 includes a projection lamp 1, a cooling fan 2, a light valve 3, and a projection lens 4. Projection light from the projection lamp 1 constituting the light source is modulated by the light valve 3, and is projected in an enlarged state by the projection lens 4 onto the screen 6.
The projection unit 20 has a closed structure except for having an intake port 201 for the cooling fan 2 and an opening 202 leading to the cooling fan 2.
In FIG. 14, the projection unit 20 is shown with the upper side being opened for purposes of illustration.
As the projection lamp, a short arc ultra-high pressure mercury lamp or the like is used in many cases.
The projection lamp attains a very high temperature. In particular, both an arc tube and a reflector, which constitute the projection lamp, attain a very high temperature.
As shown in FIG. 14, in the projection unit 20 also, the cooling fan 2 is arranged in the vicinity of the projection lamp 1, and further, the intake port 201 is formed, so the projection lamp 1 is cooled by the cooling fan 2, and air whose temperature has been raised is discharged to the outside of the projection unit 20.
Examples of the projection lamp cooling method using a cooling fan are disclosed in Japanese Patent application Laid-Open Nos. H11-39934 and 2000-82321.
As shown in FIG. 14, a cooling air A1 generated by taking in air through the intake port 201 cools the projection lamp 1 to become a hot air A2 of high temperature.
The discharge of the hot air to the outside of the projection unit 20 as described above means that the hot air is discharged into the inside of the housing 50. As a result, the temperature inside the housing rises, and the other components disposed in the housing 50 are heated, which adversely affects the performance of the projection-type display device. Further, the heat is also imparted to the light valve 3, which is disposed together with the projection lamp inside the optical unit (projection unit).
In view of this, the present inventor has made an attempt to discharge the hot air A2 used for cooling the projection lamp 1 directly from the projection unit 20 to the outside of the projection-type display device through an exhaust port (not shown) provided in the housing 50.
In this regard, in order that the position of the exhaust port of the housing 50 may be determined arbitrarily without involving any temperature rise in the housing 50, the present inventor has studied a display device which is constructed such that the hot air A2 is discharged to the outside of the projection-type display device by use of an exhaust duct 22.
However, there is a possibility, because of the hot air A2, that an object existing in the vicinity of the exhaust port of the housing 50 (e.g., a wall of a room in which the projection-type display device is installed, a furniture such as a desk, or a person using the projection-type display device to perform presentation, etc.) may be subjected to a high temperature.